The proposal provides for the Coordinating Center of the Macular Photocoagulation Study, a collaborative project to evaluate the efficacy of argon laser photocoagulation therapy in preventing loss of visual acuity in patients with presumed ocular histoplasmosis and in patients with senile maculopathy. Two randomized controlled clinical trials will be conducted under a single study organization with approximately ten clinics, a Reading Center and a Coordinating Center. It is anticipated that 500 patients will be recruited over a two-year period in the Senile Maculopathy Study and that 750 patients will be recruited into the Ocular Hisotplasmosis Study over a three year period. Therapy will consist of obliteration of parafoveal neovascular membranes in patients assigned to the treatment group.